Cardiovascular factors explain genetic background differences in VO sub(2)max

The purpose of this study was to further explore factors that may be related to ethnic differences in the maximum rate at which an individual can consume oxygen (VO sub(2)max) between 20 African American (AA) and 30 European American (EA) sedentary women who were matched for body weight (kg) and fat-free mass (FFM). VO sub(2)max (l/min) was determined during a graded treadmill exercise test. Submaximal steady-state heart rate and submaximal VO sub(2) were determined at a treadmill speed of 1.3 m/sec and a 2.5% grade. Hemoglobin (Hb) was determined by the cyanide method, muscle oxidative capacity by super(31)P magnetic resonance spectroscopy (ADP time constant), and FFM (kg) by dual-energy x-ray absorptiometry. Genetic classification was self-reported, and in a subset of the sample (N = 32), the determinants of ethnicity were measured by African genetic admixture. AA women had significantly reduced VO sub(2)max, Hb levels, and muscle oxidative capacity (longer ADP time constants, P [le] 0.05) than EA women. Submaximal oxygen pulse (O sub(2)Psubmax), ADP time constant, Hb, and ethnic background were all significantly related to VO sub(2)max (ml/kg/min and ml/kg FFM/min, all P [le] 0.01). By multiple regression modeling, Hb, O sub(2)Psubmax, muscle oxidative capacity, and ethnicity were found to explain 61% and 57% of the variance of VO sub(2)max in ml/kg/min and ml/kg FFM/min, respectively. Muscle oxidative capacity and O sub(2)Psubmax were both significantly and independently related to VO sub(2)max in all three models (P [le] 0.05), whereas Hb and ethnicity were not. These results suggest that mitochondrial muscle oxidative capacity and oxygen delivery capabilities, as determined by O sub(2)Psubmax, account for most if not all of the ethnic differences in VO sub(2)max. Am. J. Hum. Biol. 18:454-460, 2006.